The expense of such aid may be paid from one or more of the following:
(a) The county general fund.
(b) The road fund.
(c) The proceeds of any county bond issue voted for the purpose of laying out, constructing, maintaining, improving or repairing county highways or for the acquisition of any real property or interest therein, rights of way or other property necessary for such purposes.
(d) Any other fund available for such purposes.